Thermally compensated standpipe assembly for automatic transmission oil fill

Abstract

A standpipe assembly for installation in the fluid sump of a vehicular transmission includes a two-piece fill pipe, a drain nut, a drain plug and a thermal actuator. The fill pipe includes a first tube having a first end secured in a flow passage formed in the drain nut and a second tube having a first end fitted for bi-directional sliding movement on a second end of the first tube. The drain nut is secured within a mounting bore formed through a housing of the transmission. The drain plug is adapted for threaded retention within the flow passage of the drain nut. The thermal actuator is operable for varying the length of the fill pipe by adjusting the position of the second tube relative to the first tube in response to thermal variations.

1. In a transmission for a motor vehicle having a housing defining a fluid sump and a mounting bore communicating with the sump, a standpipe assembly comprising:
 a first tube extending from the mounting bore so as to extend into the sump, said first tube defining a first flow passage and a first uniform outer diameter along its length; 
 a second tube having a first end and a second end supported for sliding movement relative to said first tube and defining a second flow passage which communicates with said first flow passage, said second tube defining a second uniform outer diameter along its entire length; 
 a threaded drain nut having an outer wall surface defining a mounting diameter adapted for engagement with threads formed in the mounting bore for securing said drain nut to the housing, said mounting diameter being at least equal to said first and second outer diameters, respectively; and 
 a thermal actuator operable for biasing the second tube in a first direction to vary the position of said second tube relative to said first tube in response to changes in the temperature of fluid in the sump, wherein said thermal actuator engages said first end of said second tube and said threaded drain nut. 
 
     
     
       2. The standpipe assembly of  claim 1  wherein said first tube has a first end secured to the housing and a second end, said second tube has a first end disposed for sliding movement on said second end of said first tube and a second end defining an inlet to said second flow passage. 
     
     
       3. The standpipe assembly of  claim 2  wherein said thermal actuator surrounds said first tube and engages said first end of said second tube, said thermal actuator operable for moving said inlet of said second tube from a first position to a second position in response to a change in the fluid temperature in the sump increasing from a first temperature value to a second temperature value. 
     
     
       4. The standpipe assembly of  claim 3  wherein movement of said inlet of said second tube to its second position corresponds to a higher fluid level in said sump. 
     
     
       5. The standpipe assembly of  claim 3  wherein said thermal actuator is a coil spring made from a material capable of varying length dimension of said coil spring in response to variations in the temperature of the fluid in the sump. 
     
     
       6. The standpipe assembly of  claim 5  wherein said coil spring is made from a bi-metallic material. 
     
     
       7. The standpipe assembly of  claim 1  further comprising:
 a drain plug adapted for retention in said drain port of said drain nut to prevent fluid from draining out of the housing; and 
 wherein said first tube is secured to said drain nut with its first flow passage communicating with a drain port through said drain nut. 
 
     
     
       8. The standpipe assembly of  claim 1  wherein said second tube has an end segment which surrounds an end segment of said first tube, said end segment of said first tube includes a radial flange having an end surface facing an inner wall surface of said second tube, and wherein said end segment of said second tube includes a radial flange having an end surface facing an outer wall surface of said first tube. 
     
     
       9. The standpipe assembly of  claim 8  further including a biasing spring disposed between said radial flanges of said first and second tubes. 
     
     
       10. In a transmission for a motor vehicle having a housing defining a fluid sump and a mounting bore communicating with the sump, a standpipe assembly comprising:
 a first tube extending from the mounting bore so as to extend into the sump, said first tube defining a first flow passage and a first uniform outer diameter along its length; 
 a second tube having a first end and a second end supported for sliding movement relative to said first tube and defining a second flow passage which communicates with said first flow passage, said second tube defining a second uniform outer diameter along its length; 
 a threaded drain nut having an outer wall surface defining a mounting diameter adapted for engagement with threads formed in the mounting bore for securing said drain nut to the housing, said mounting diameter being at least equal to said first and second outer diameters, respectively; and 
 a bimetal spring interposed between said second tube and said threaded drain nut and operable for biasing said second tube in a first direction to vary the position of said second tube relative to said first tube in response to changes in the temperature of fluid in the sump, wherein said bimetal spring engages said first end of said second tube and said threaded drain nut. 
 
     
     
       11. The standpipe assembly of  claim 10  wherein said first tube has a first end secured to the housing and a second end, said second tube has a first end disposed for sliding movement on said second end of said first tube and a second end defining an inlet to said second flow passage. 
     
     
       12. The standpipe assembly of  claim 11  wherein said bimetal spring surrounds said first tube and engages said first end of said second tube, said bimetal spring operable for moving said inlet of said second tube from a first position to a second position in response to a change in the fluid temperature in the sump increasing from a first temperature value to a second temperature value. 
     
     
       13. The standpipe assembly of  claim 12  wherein movement of said inlet of said second tube to its second position corresponds to a higher fluid level in said sump. 
     
     
       14. The standpipe assembly of  claim 12  wherein said bimetal spring is made from a material capable of varying a length dimension thereof in response to variations in the temperature of the fluid in the sump. 
     
     
       15. The standpipe assembly of  claim 10  further comprising:
 a drain plug adapted for retention in said drain port of said drain nut to prevent fluid from draining out of the housing; and 
 wherein said first tube is secured to said drain nut with its first flow passage communicating with a drain port through said drain nut. 
 
     
     
       16. The standpipe assembly of  claim 10  wherein said second tube has an end segment which surrounds an end segment of said first tube, said end segment of said first tube includes a radial flange having an end surface facing an inner wall surface of said second tube, and wherein said end segment of said second tube includes a radial flange having an end surface facing an outer wall surface of said first tube.